Unable to connect to Vagrant private network from host

Based on the output provided, the box has 2 network interfaces, 1 is the default NAT and the other private - ask you said.

The reason why you are not able to access the web site hosted within the VM thru the private interface: it could be that host eth0 or wlan0 IP address is not in the same network as the private interface -> 192.168.50.4/24 and there is no route.

To access the the site hosted by the web server within the guest, you have the following options:

1. NAT port forwarding

Forward the web port, e.g. 80 to host's 8080 (you can't use 80 because it is a privileged port on *NIX). Add the following

Vagrant.configure("2") do |config|
  config.vm.network "forwarded_port", guest: 80, host: 8080,
    auto_correct: true
end

NOTE: auto_correct will resolve port conflicts if the port on host is already in use.

DO a vagrant reload and you'll be able to access the site via http://localhost:8080/

2. Public Network (VirtualBox Bridged networking)

Add a public network interface

Vagrant.configure("2") do |config|
  config.vm.network "public_network"
end

Get the IP of VM after it is up and running, port forwarding does NOT apply to bridged networking. So you'll be accessing the site by using http://IP_ADDR, if within the VM it binds to 80, otherwise specify the port.

One more possibility just for future reference.

Normally when you create VMs using private networking, Vagrant (Virtualbox? not sure) creates corresponding entries in the host's routing table. You can see these using

netstat -rn

Somehow my host had gotten into a state where creating the VMs did not result in new routes appearing in the routing table, with the corresponding inability to connect. Again you can see the routes not appearing using the command above.

Creating the route manually allowed me to reach the VMs. For example:

sudo route -nv add -net 10.0.4 -interface vboxnet

(Substitute the appropriate network and interface.) But I didn't want to have to do that.

Based on this question, I tried restarting my host and Vagrant started automatically creating the routing table entries again.

Not sure exactly what the issue was, but hopefully this helps somebody.

Your interface is down

I had the same issue. It was my vboxnet0 interface who was down. Within the listing of ip addr you have <BROADCAST,MULTICAST> for your interface but it should be <BROADCAST,MULTICAST,UP,LOWER_UP>.

That's mean you interface is down.

You can confirm with sudo ifconfig. The interface will not be shown but if you add -a you will see it : sudo ifconfig -a.

how to bring it up

So to bring it up you can do :

sudo ifconfig vbox

OR

sudo ip link set vboxnet0 up

Both works.